if you want to set the text size/pixel density in firefox different from that of your system's settings like it was handled in prior versions, enter about:config into the firefox address bar (confirm the info message in case it shows up) & search for the preference named layout.css.devPixelsPerPx. double-click it and change its value to 1.0 (or any other zoom factor that fits your purpose; -1.0 is the default value and will adhere to the system settings).

if you want to set the text size/pixel density in firefox different from that of your system's settings like it was handled in prior versions, enter about:config into the firefox address bar (confirm the info message in case it shows up) & search for the preference named layout.css.devPixelsPerPx. double-click it and change its value to 1.0 (or any other zoom factor that fits your purpose; -1.0 is the default value and will adhere to the system settings).

hello, firefox 22 is now respecting the pixel density you've set on a system level in the windows control panel > appearance > display. more information about that is available at http://windows.microsoft.com/en-us/windows7/make-the-text-on-your-screen-larger-or-smaller
if you want to set the text size/pixel density in firefox different from that of your system's settings like it was handled in prior versions, enter '''about:config''' into the firefox address bar (confirm the info message in case it shows up) & search for the preference named '''layout.css.devPixelsPerPx'''. double-click it and change its value to '''1.0''' (or any other zoom factor that fits your purpose; -1.0 is the default value and will adhere to the system settings).